Acoustic vibrato device for electronic organ



T. J. GEORGE 2,780,302

ACOUSTIC VIBRATO DEVICE FOR ELECTRONIC ORGAN Feb. 5, 1957 2 Sheets-Sheet1 Filed Aug. 8, 1955 IN VEN TOR.

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y llin ki w T. J. GEORGE 2,780,302

ACOUSTIC VIBRATO DEVICE FOR ELECTRONIC ORGAN Feb. 5, 1957 2 Sheets-Sheet2 Filed Aug. 8, 1955 FIG. 6

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ACOUSTIC VKBRATO DEVEE FGR ELECTRGNI ORGAN Thomas J. George, hasAug-ales, Application August 8, 1955, Serial No. 527,013

15 Claims. (Cl. 18131) The present invention relates in general to loudspeaker enclosures and in particular to reproducers for electronicorgans.

There are two general methods in common usage for imparting vibrato tothe tones of the electronic organ. One involves periodically changingthe pitch or amplitude of the tones by entirely electronic means. Thisis an electronic vibrato. The other operates to modify the organ tonesissuing from the reproducing speaker by mechanical or acoustical means.This is an acoustic vibrato. The present disclosure relates to thesecond method.

It is well known that the use of vibrato in the playing of organ musicadds richness and appeal to the music. This is especially true ofballads and so called popular music. This type of organ music achievedconsiderable popularity during the time when the theatre pipe organ,with its heavy vibrato, was common.

The vibrato is obtained in the pipe organ by a rising and fallingpressure in the wind supply which is blowing the pipes. This causes boththe ampltiude and pitch of the pipe tones to rise and fall, thusproducing the vibrato.

The electronic organ has now become more common, especially forentertainment purposes, and for music of this type a heavy theatricalvibrato is often desirable. According to tone quality classifications,there are two major classes of such organs. One includes those whichproduce tones which are essentially flute-like in character, which tonesare added together in various ways to produce tones of more complexcharacter. The other class includes those electronic organs in which thetones as produced, are complex, and have many natural harmonics. Theselatter tones include such voices as reed and string tones.

A successful means for obtaining a heavy acoustic vibrato with theflute-like tones is in common usage, and involves passing the tones fromthe organ speaker through a revolving horn (see Leslie 2,489,653). Thisarrangement, however is not very successful with the class of organsgenerating complex .ones. Accordingly, it is a principal object of thisinvention to provide means for obtaining a heavy acoustic vibrato withorgans generating complex tones, as well with organs which produce theflute-like tones.

The normal vibrato rate is from approximately six to seven beats persecond. It has een found in the structure of the present disclosure thatin addition to the normal or primary vibrato beat, a secondary vibratobeat, spaced in time between primary beats is very desirable. lt istherefore a ftnther object of this invention to provide means forobtaining a secondary beat in addition to the normal vibrato beat.

Another object of the invention is to employ a moving acousticresonating chamber to further enhance the vibrato effect.

Another object is to employ a fixed acoustic resonating chamber toincrease the vibrato eifect.

Another object is to provide an organ tone cabinet nited States Patent"ice which, in conjunction with the vibrato which it produces, imparts acharacteristic timbre to the tones.

Another object is to disclose how the invention can be used toadvantage, in a tone cabinet for a church organ, and in a tone cabinetfor an entertainment organ.

Another object is to provide means for producing the heaviest usefulvibrato for the entertainment organ.

Other objects will appear from the following description, referencebeing had to the accompanying drawings, in which;

Figure vention.

Figure 2 is a diagrammatic end view of the structure shown in Figure 1.

Figure 3 is an improved form of rotor for the invention.

Figure 4 is another improved form of rotor.

Figure 5 is a diagrammatic end view of one form of the invention.

Figure 6 is a diagrammatic end view of another form of the invention.

Figure 7 is a diagrammatic end view of another form of the invention.

Figure 8 is a diagrammatic end view of another form of the invention.

In Figure l is shown a pictorial View of a speaker enclosure or tonecabinet, embodying one form of the in vention. A horizontal speakerboard 1 supports loud speakers 2, and is mounted upon an enclosurehereinafter referred to as the rear battle, and which in this case is abox 3, entirely enclosed, excepting for the open port 4, near the bottomand at the rear of the enclosure. Above the speaker board are two endwalls 5 and s, and rear wall 7. These three walls in coniunction wit.the speaker board 1, form four sides of a box which is hereinaftercalled the front battle, and will appear in modified forms, as shown inthe other figures. A fiat wooden vane 8 called the rotor, and mountedupon shafts 9, is rotatably supported in bearings 16. By means ofelectric motor 13, pulley 11, and belt 1.2, the rotor is caused torotate at a rate of approximately three revolutions per second. By meansof a signal source, such as an electronic organ and an amplifier (notshown), signals are impressed upon the voice coils of the loud speakers.The tones issuing from the speakers are acoustically influenced by therotating vane, and a very pleasing vibrato is imparted to the tones.Note that to produce a vibrato of six beats per second the shaft rotatesthree times per second. This occurs because any given angular positionof the rotor occurs twice in one revolution of the shaft.

The requirements for successful design of a structure in accordance withthe invention are as follows. The

" in Figures 1 and 2 should be at l is a pictorial view of one form ofthe inrear battle enclosure .3 least partially open for best frequencyresponse characteristics. A completely enclosed rear bafile produces theheaviest vibrato, but the frequency response is somewhat restricted foraverage requirements.

A second requirement is that the front bafile should be partiallyenclosed. In Figures 1 and 2 the front baille is comprised of thespeaker board 1, the two end walls 5' and 6, and the rear wall 7, thusforming a box-like structure in which the front and top are open. Otherfigures will show how the front and top may be partially enclosed toprovide different vibrato effects.

A third requirement is that the rotor vane of Figures 1 and 2 should benearly as large as the speaker board 1. Thus as shown in Figure 2 whenthe bearings are centrally located in the end walls 5 and 6, theclearance A between the rear wall 7 and the edge of the rotor vane 8when in the horizontal position, should be as small as is practicallypossible. Approximately one quarter inch will meet this requirement.Similarly, the clearance B in Figure 5 between the edge of the rotor inthe vertical position, and the speaker board should be not more thanapproximately one quarter inch. These three requirements cooperate inthis structure to produce a vibrato (or tremulant) which includes threeacoustic effects. The first is a periodic change in pitch of the tones;the second is a periodic change in intensity of the tones; and the thirdis a periodic change in the timbre of the tones. These are the samethree effects which are produced in the tones from organ pipes, when thewind pressure is raised and lowered to produce vibrato.

Another effect which has been found to enhance the vibrato is theintroduction of a secondary vibrato beat in addition to the normal orprimary vibrato beat. These secondary beats are of somewhat lesseramplitude, and are spaced alternately in time between the primary beats.Figure 3 illustrates a modified form of rotor designed to produce asecondary beat in addition to the normal vibrato beat, and which may besubstituted for the single rotor vane 8. 'In addition to the large vane8 as shown in Figures 1 and 2, two smaller vanes 14 are mounted at rightangles to, and along the center line of the main vane. These vanesshould be slightly wider (measured at right angles to the shafts) thanhalf the Width of the large vane 8. Thus if vane 8 measures 12 inchestip to tip, then the two smaller vanes (measured from tip to tip),should measure approximately seven and one half inches. With thisarrangement the secondary beat is less prominent than the primaryvibrato beat. The smaller rotor vanes should not be made too large, forthen the secondary beat becomes too prominent. This is very undesirable.The secondary beat should never be more than just barely audible as asecondary beat for greatest effectiveness. The secondary beat has theeffect of filling out the vibrator cycle; making it heavier andsmoother. It has an equally important effect in the treble range of theorgan as follows: other widely used acoustic type vibrato systems have adecided tendency to. introduce in the treble range extraneous sounds andbeats, which are not pleasant. Since this is the range where most of theharmonics lie in organs generating complex tones, these systems have notproven successful when used with organs of this class. An outstandingfeature of the present invention is that it imparts a very pleasing andheavy vibrato to the tones in the treble range without introducingundesirable extraneous sounds.

This improvement is due in part to the secondary beat feature, and inpart to the use of acoustic resonators. In one form, the resonator is infixed position, and in the other form the resonator is in motion, and isa component part of the rotor.

Referring to Figure 2, the rotor vane is shown in dashed lines 16 in anintermediate angular position of rotation of approximately 45 degreesfrom vertical. Figure I shows the rotor in approximately the sameposition. In this position a partially enclosed resonator is formed bythe three plane surfaces comprising speaker board 1, back Wall 7, andthe rotor vane. The end walls 5 and 6 complete this enclosure. Thespeaker is coupled to this resonator, and for a brief interval, as therotor passes through this position, the frequency response of the systemis altered somewhat. A change of timbre thus becomes a component of thevibrato cycle. In this position also, there is a reduction in audiooutput level, thus introducing some degree of tremulant into the vibratocycle. A rise and fall in pitch is simultaneously taking place, due tothe Doppler effect, as the vanes rotate toward and away from thespeakers. The three effects therefore combine to produce a satisfyingand organlike vibrato.

Acoustic resonators have been widely used in speaker enclosures for bassfrequency reinforcement, and even for high frequency reinforcement, butI am not aware of the use of acoustic resonators for intentionallyand-periodically altering the character of tones produced.

These eifects may be modified in various ways, as

shown in the other figures, to produce other and useful effects invibrato and tone color variations.

The effectiveness of the fixed resonator just described, may beincreased by the addition of a partial top 15 to the front baffle. Thisis shown in Figure 5. The resonator thus formed when the rotor is in thevertical position as shown, is more enclosed due to the smallerclearances at B and C. It is therefore a more effective resonator. Alsothe speakers are more closely coupled to the resonator. The result ofthis change is to produce a heavier vibrato by increasing the amount ofchange of timbre.

Figure 4 illustrates another form of rotor which is even more effectivethan that shown in Figure 3. This rotor may be used in place of eitherrotor previously described. The requirement for minimum clearances withthe front bafiie walls still applies. In this rotor the large flat vane8 has been replaced by a resonator box 17 which is open at both top andbottom. The shorter vanes 14 have been replaced by longer vanes 13 toprovide a heavier secondary beat. Figure 6 is a diagrammatic end view ofthe tone cabinet, showing the rotor of Figure 4 in position. The partialtop 15 should extend approximately to the near edge of the resonator 17when the resonator is in its vertical position. In this rotor the tip totip dimension of the vanes 18 should be the same as the tip to tipdimension of the resonator 17, measured at right angles to the shafts 9.

Figure 8 illustrates a diagrammatic view of one form of the inventionwhich provides the maximum usable vibrato. In this case the rear bafile3 is a box, entirely enclosed. Mounted above the speaker 2 and restingupon the speaker board 1, is a resonator box 22. This resonator hassloping sides and is shaped like a hollow Wedge, with the top open toprovide egress for the tones from the speaker. The rotor of Figure 4having the resonator 17 is used, and when the resonator is in thevertical position as shown in the figure, the action of the tworesonators is similar to that of a funnel, so that nearly all the soundfrom the speaker is carried upward and out of the top opening ofresonator 17. To further increase this efiect the top of the baffie iscovered excepting for an opening immediately above the opening in theresonator 17. This is accomplished by means of the partial top memhers15 .and 20. Also a partial front 19 has been installed to cover theupper portion of the front baflie.

During the interval when the rotor 17 is approaching and leaving thevertical position, there i a very marked change in the amplitude andtimbre, as well as the pitch of the tones issuing from the speaker, withthe result that the structure provides a very heavy vibrato. Also it hasseveral peaks in its, frequency response characteristic, which may beused to advantage.

The vox humana organ voice is very beautiful and is widely used. Evenfor church organ use, heavy vibrato is always employed With the voxhumana. Normally the vox humana harmonic distribution is approximatelyas follows: weak in the fundamental harmonic and any frequencies below afew hundred cycles; moderately strong in the higher frequencyharmonicsbetween two to four thousand cycles; and with .a pronouncedpeak in the region between thirteen hundred to fifteen hundred cycles.This is quite similar to th frequency response characteristic of thestructure illustrated in Figure 8. When the vox humana voice of anelectronic organ is played through a tone cabinet of this construction,the effect i exceedingly realistic, and closely resembles the vox humanavoice of the pipe organ. Other reed voices such as oboe and Englishhorn, as well as the string voices, are also enhanced when playedthrough this type tone cabinet.

In Figure 7 is illustrated another modified form of the invention. Therear baffle 3 may be completely or partially enclosed. Any of the threerotors disclosed may be used, and the one of Figure 3, having the largevane 8 and the short vanes 14 is shown. The front baffie is d shownentirely enclosed excepting for the open top, a front wall 21?. havingbeen added to the structure shown in Figure 1. In this arrangement thechange in intensity or tremulant, during the vibrato cycle is morepronounced than in any of the other structures shown.

Although in this description the secondary vibrato beat has beenconsidered only as a secondary beat of the same periodicity as theprimary vibrato beat, it might also be thought of as introducing adouble vibrato rate component into the overall vibrato cycle; and infact the maximum effectiveness is obtained when the double beat is justbarely apparent as such.

It will be seen from the foregoing that there are numerous combinationsor" the six basic features disclosed, which may be utilized to provide aplurality of interesting and useful effects in electronic organ tonecabinets, for both church use and entertmnment use.

The number of loud speakers actually used in the tone cabinet is notimportant so long as the other require ments laid down are met.

In summary, the six basic features disclosed are:

(l) A partially enclosed front baffle.

(2) Enclosed and partially enclosed rear bafile.

(3) Fixed resonator chamber coupled to the speaker.

(4) Resonator chamber in rotor.

(5) Minimum clearance between the rotor and the walls of the frontbaffle.

(6) The secondary vibrato beat added to the normal vibrato beat.

I am aware that in the prior art, moving horns, vanes, speakers, drums,and deflectors, have been used to produce acoustic vibrato, but I am notaware that any of them have been used in structures similar to thosedisclosed herein, or that any of them have been as effective with organtones of complex character as the present disclosure. And in fact,almost any of the prior art structures would be improved by the additionof the secondary vibrato beat feature.

Although for the purpose of illustrating and describing the inventioncertain preferred embodiments have been shown, it will be apparent tothose skilled in the art that variou modifications can be made, such asthe use of different rotor shapes, or different bafiie configurations,without departing from the basic principles of the invention. 1therefore do not wish to be limited to the precise details set forthherein, but desire to include within the scope of the invention thosemodified forms by means of which similar result may be obtained insubstantially the same way.

Having thus described my invention, I claim as follows:

1. In a tone cabinet for an electronic organ, a baflie enclosure, aspeaker, a rotor for influencing sound from said speaker, means forrotating said rotor, said rotor comprising a main deflecting means, anda secondary deflecting means, said main deflecting means operating toproduce a vibrato beat of one intensity, said secondary deflecting meansoperating to produce a secondary vibrato beat of lesser intensity.

2. in a sound radiating device of the class described, acousticradiating means, means for restricting the radiation of sound in onedirection, .eans for periodically altering t1 e sound radiated inanother direction, said latter means comprising means for imparting afirst acoustic beat of normal vibrato rate, and a secondary acousticbeat, to the radiated sound.

3. In a device of the class described, a bafiie enclosure, a loudspeaker, means for imparting acoustic vibrato to the tones issuing fromloud speaker, means for causing said acoustic vibrato to have primarybeats of one intensity and secondary beats of lesser intensity, saidprimary beats and said secondary beats being alternately spaced in time.

4. in a tone cabinet for an electronic organ, a horizontal speakersupport, a partially enclosed rear baffle, a speaker, a front bafile, arotor, said speaker mounted upon said speaker support, with the body ofsaid speaker within said rear baffle, said front baffle comprising twoend Walls and a rear wall vertically mounted upon said speaker supportand a horizontal top member partially covering the top opening of saidbame, said horizontal top disposed rearward and adjacent said rearvertical wall, bearing means centrally located in said end walls, saidrotor rotatably mounted in said bearings, mechanical means for rotatingsaid rotor, the outermost edges of said rotor While in rotation, passingwithin approximately one quarter inch in each case, the surfaces of saidspeaker support, said vertical rear wall, and said horizontal topmember, said rotor comprising means for causing a primary vibrato beatof one intensity and a secondary vibrato beat of a lesser intensity.

5. The combination set forth in claim 4 in which said rotor incorporatesan acoustic resonator.

6. in a tone cabinet for an electronic organ, a partially enclosed rearbafile, a horizontal speaker mounting board, a speaker mounted thereon,a partially enclosed front bafiie having four sides mounted verticallyupon said speaker mounting board and forming a five sided box the top ofwhich is open, bearing means centrally mounted in opposite ends of saidbox, a rotor comprising an acoustic resonating chamber, said rotorrotatably mounted in said bearings, the dimensions of said rotor beingsuch that while it is in rotation the minimum practical clearance existsbetween the edges of the rotor and the Walls of said box, means formechanically rotating said rotor.

7. In a tone cabinet for an electronic organ, a partially enclosed rearbafiie, a partially enclosed front baffle, a speaker mounting support, aspeaker mounted thereon, rotor, bearing mounting means for said rotor,means for rotating said rotor, said rotor comprising two fiat vanes setat right angles to each other, one of said vanes being larger than theother.

8. in a tone cabinet for an electronic organ, a partially enclosed rearbattle, a partially enclosed front battle, a speaker mounting support, aspeaker mounted thereon, a rotor, bearing mounting means for said rotor,means for rotating said rotor, said rotor comprising an acousticresonating chamber having at least three plane surfaces.

9. In a tone cabinet for an electronic organ, a horizontal speakermounting board, an enclosed rear baffie, a speaker, a rotor, a partiallyenclosed front baffie, said speaker mounted upon said speaker board withthe body of said speaker within said enclosed rear baffle, said frontbafile comprising a six sided box, said speaker board forming the bottomof said box, bearng means centrally located in the opposite end walls ofsaid box, said rotor rotatably mounted in said bearings, an opening inthe top of said box opposite to said speaker, an opening in one of thesides of said box adjacent said speaker board, a fixed acousticresonator located within said box and closely coupled to said speaker,said rotor incorporating a channel means of such configuration that whensaid rotor is in its vertical position sound is conducted from saidspeaker via the channel to the opening in said top, and mechanical meansfor rotating said rotor.

10. The combination set forth in claim 9 in which said fixed resonatoris shaped like a hollow wedge having the top open to provide egress forthe tones from said speaker.

11. In a device of the class described, at least one loud speaker,enclosure means serving both as an acoustic bathe and as means forrestricting radiation of sound from one side of said speaker, meansincluding fixed rear surface of said speaker, cooperative means forinfiuencing sound flowing from the front surface of said speaker, saidcooperative means comprising both fixed and movable members, said fixedmembers mounted upon said supporting means in a plane normal with theaxis of said speaker, said movable member rotatably mounted in a planeat right angles to the axis of said speaker and closely adjacent saidsupporting means and said fixed members, said fixed members and saidmovable member cooperating to form a partially enclosed acousticresonator during at least part of a revolution of said movable member.

13. The combination set forth in claim 12 in which said movable membercomprises means for producing a primary influence and a secondaryinfluence upon the sound flowing from the speaker.

14. The combination set forth in claim 12 in which said movable membercomprises an acoustic resonator chamber having at least three planesurfaces.

15. In a tone cabinet for an electronic organ, speaker supporting meansforming the upper surface of a box-like baflie enclosure, said enclosurehaving an opening along the lower edge'of one wall, speakers mountedupon the underside of said support means and directed upward, means forintroducing an acoustic vibrato into the tones issuing from saidspeakers, said means comprising fixed members and a movable member, saidfixed members comprising three walls mounted vertically upon saidsupport means, and forming therewith four sides of a partial enclosure,the two opposite of said three walls having bearings means centrallymounted therein, said movable member comprising a narrow box shapedacoustic resonator open at top and bottom, and having a fiat vanemounted longitudinally upon, and at right angles to, each of its longsides, said movable member being rotatably supported in said bearingmeans, mechanical means to cause said movable member to rotate.

References Cited in the file of this patent UNITED STATES PATENTS 73,719Hitchcock Jan. 28, 1868 360,857 Crandall Apr. 12, 1887 2,062,515 HoschkeDec. 1, 1936 2,412,212 Gerlat Dec. 10, 1946

